Aquatic and Wetland Vascular Plants of the Northern Great Plains

Spiranthes Rich. -- Ladies'-tresses

Slender, erect, mostly glabrous plants from a cluster of tuberous roots. Leaves best developed at the base, reduced and bractlike upward, the cauline leaves appressed and sheathing. Flowers small, usually many, arranged in usually (1)2-4 spirally twisted rows in a dense, bracteate spike, white or cream-colored; sepals and lateral petals similar, the lateral petals connivent with all 3 sepals or only with the upper one to form a hood over the lip and column; lip oblong or ovate, folded upward near the middle so that the margins embrace the column, curved downward beyond the middle, with a pair of protuberances or thickenings at the base; anther 1, borne on the back of the short column.

Reference:
  
Sheviak, C. J.  1973.  A new Spiranthes from the grasslands of central 
     North America.  Bot. Mus. Leafl. 23:285-297.

Lead	Characteristic	Go To
1	Lateral petals connivent with all 3 sepals to form a hood, the lateral sepals not free; lip with a distinct constriction at ca. 3/4 of its length resulting in a round-ovate terminal lobe, the base of the lip with a pair of lateral thickenings but these not projecting*.	S. romanzoffiana
1	Lateral petals connivent with only the upper sepal to form a hood, the lateral sepals free on the sides; lip not constricted or only slightly so near the middle, without a distinct terminal lobe, the base of the lip with a pair of backward projecting protuberances.	Lead 2
2	Flowers in a single spiral in the spike.	Lead 3
2	Flowers in 2-4 spirals in the spike.	Lead 4
3	Pubescence in the inflorescence with knoblike, glandular tips; lip smooth to glandular on the underside.	S. cernua
3	Pubescence in the inflorescence sharp-tipped; lip prominently papillate on the underside.	S. vernalis
4	Leaves becoming brown and dried by flowering time; lip not constricted near the middle.	S. magnicamporum
4	Leaves mostly remaining green at flowering time; lip slightly constricted near the middle.	S. cernua

*If working with dried material, flowers must be soaked in a wetting solution for several minutes or boiled in water to facilitate dissection.

69. Orchidaceae, the Orchid Family

5. Spiranthes Rich. -- Ladie's-tresses

1. Spiranthes cernua (L.) Rich. -- Nodding ladies'-tresses

2. Spiranthes magnicamporum Sheviak -- Great Plains ladies'-tresses

3. Spiranthes romanzoffiana Cham. -- Hooded ladies'-tresses

4. Spiranthes vernalis Engelm. & A. Gray -- Spring ladies'-tresses

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